Reactor surface passivation through chemical deactivation

Abstract

Protective layers are formed on a surface of an atomic layer deposition (ALD) or chemical vapor deposition (CVD) reactor. Parts defining a reaction space for an ALD or CVD reactor can be treated, in situ or ex situ, with chemicals that deactivate reactive sites on the reaction space surface(s). A pre-treatment step can maximize the available reactive sites prior to the treatment step. With reactive sites deactivated by adsorbed treatment reactant, during subsequent processing the reactant gases have reduced reactivity or deposition upon these treated surfaces. Accordingly, purge steps can be greatly shortened and a greater number of runs can be conducted between cleaning steps to remove built-up deposition on the reactor walls.

Description

REFERENCE TO RELATED APPLICATION[0001]This application claims the priority benefit under 35 U.S.C. §119(e) to provisional patent application No. 60 / 469,181, filed May 9, 2003.FILED OF THE INVENTION[0002]The present invention generally relates to inhibiting deposition on reactor surfaces in chemical vapor deposition (CVD) and atomic layer deposition (ALD) reactors. More specifically, the present invention relates to de-activating a surface of the reactor to limit coating by subsequent gases flowing through the reactor.BACKGROUND OF THE INVENTION[0003]Atomic layer deposition (ALD) is a known process in the semiconductor industry for forming thin films of materials on substrates such as silicon wafers. ALD is a type of vapor deposition wherein a film is built up through self-saturating reactions performed in cycles. The thickness of the film is determined by the number of cycles performed. In an ALD process, gaseous precursors are supplied, alternatingly and repeatedly, to the substrat...

AI Technical Summary

Benefits of technology

[0014]In accordance with another aspect of the invention, a deposition system is provided with a reactor that has a deposition chamber for depositing a film onto a substrate. Surfaces of the deposition chamber is coated with reactive sites selected from the group consisting of —OH, nitrogen, hydrogen and halide surface groups. A substrate support is located within the reactor and configured to support the substrate. A treatment gas source contains a treatment gas. An inlet line in flow communication with the treatment gas source is configured to supply the treatment gas to the surfaces of the deposition chamber. The treatment gas is selected to bind to the reactive sites to form a protective layer on the surfaces of the deposition chamber, which protective layer reduces the likelihood of the film depositing on the surfaces of the deposition chamber.

[0015]In the illustrated embodiments, the deactivation is provided by adsorption of treatment reactants upon reaction space surfaces. The treatment process binds available reactive sites, occupying or otherwise preventing such reactive sites from exposure to deposition reactants in subsequent processing. For example, —OH molecules are often present on the surfaces of metal reaction space surfaces and oxide-passivated metal surfaces (e.g., titanium coated with aluminum oxide). Such —OH termination readily reacts with typical ALD precursors. Similarly, other types of reactive sites can be present. A treatment gas causes adsorption of treatment reactant, binding the —OH groups and leaving a termination that is nonreactive to the particular ALD reactants that are connected to the reactor for deposition. In particular, the strength of the bond between the treatment reactant (absorbed largely intact) and the reaction space surfaces is strong enough to avoid desorption or chemical reaction with the deposition reactants.

[0016]Major benefits of the deactivation process are a considerable reduction in deposition buildup on the reaction chamber surfaces, reduced downtime for reactor cleaning and reduced particulate generation. Furthermore, time to remove reactants between deposition steps can be considerably reduced by the fact that reactants do not readily adhere to the walls. This is a particularly significant advantage for ALD, wherein removal steps (typically purging with inert gas) are repeatedly employed between each reactant pulse to avoid gas phase reactions. Deactivation of reaction space surfaces against the deposition reactions permit effective purging with greatly reduced purging times. In the context of ALD, “effective” purging entails purging such as to prevent undue risk of gas phase mixing between successive reactant pulses. This not only reduces the cycle time for an ALD step but also results in more uniform deposition films on the substrate by reducing gas phase CVD reactions.

Problems solved by technology

A shorter duration purge step can increase the available time for adsorption and reaction of the reactants within the reactor, but the vapor phase reactants are not allowed to mix to avoid the risk of CVD reactions destroying the self-limiting nature of the deposition.

The film buildup can delaminate from the reactor surfaces and contaminate the substrate surface.

Hence, this can also increase the pulse and purge time required to saturate the wafer surface

On the other hand, cooler CVD reactant parts may be subject to reactant condensation or adsorption / desorption, as in ALD reactors, leading to contamination problems again.

Frequent cleaning of the reactor can limit the potential for contamination.

However, the reactor is out of service during these cleanings and thus reduces the efficiency of the ALD or CVD process.

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